Abstract
Purpose :
Diabetic retinopathy is characterized not just by microaneurysms, capillary nonperfusion and ischemia within the retina, but also by choroidal angiopathy. Significant advances in spectral-domain optical coherence tomography (SD-OCT) and image analysis tools has not only allowed good visualization of the choroid but also of choroidal vasculature. This study was hence envisaged to prospectively analyse the changes in the choroidal architecture of patients with diabetes following cataract surgery using the well established parameter of choroidal thickness (CT)and a newly derived parameter-choroidal vascularity index (CVI).
Methods :
A prospective case control study was conducted in 18 diabetic and 18 controls undergoing phacoemulsification cataract surgery. Enhanced depth imaging (EDI) SD-OCT of the macula was obtained before and after cataract surgery. CT was measured subfoveal and at 500μm nasal and temporal to the fovea (Figure 1). Niblack’s image binarization of the OCT scans were performed to derive the total choroidal area (TCA) and luminal area (LA) from the submacular choroid (Figure 2). The CVI was obtained from the ratio of LA and TCA. The independent sample T-test was used to compare the differences of CVI and CT between diabetic and non-diabetics. Pearson’s correlation coefficient was used to study the association between CVI and CT with age, axial length, spherical equivalent and diabetic control.
Results :
The CVI was significantly reduced in diabetics compared to non-diabetics at baseline for both operated and control eyes (mean difference 0.0184, 95% CI 0.004 to 0.0324, p = 0.012; mean difference 0.0145, 95% CI 0.003 to 0.0256, p = 0.012) with no statistically significant difference in CT. CT increased following cataract surgery (diabetics: mean difference 12.4, 95% CI 0.70 to 24.0, adjusted p = 0.036; non-diabetics: mean difference 21.0, 95% CI 4.39 to 37.6, adjusted p = 0.011). There was a negative linear association between CT and axial length (r = -0.595, p = 0.009) and a positive linear association between CT and CVI with spherical equivalent (r = 0.521, p = 0.038; r = 0.597, p= 0.015).
Conclusions :
Diabetics have reduced CVI compared to controls, suggestive of possible reduction in choroidal vascularity. CT increases following cataract surgery, but there were no corresponding changes in CVI.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.